package main

type pqItem struct {
	node     *searchNode
	priority float64
	index    int
}

type priorityQueue []*pqItem

func (pq priorityQueue) Len() int { return len(pq) }

func (pq priorityQueue) Less(i, j int) bool { return pq[i].priority < pq[j].priority }

func (pq priorityQueue) Swap(i, j int) {
	pq[i], pq[j] = pq[j], pq[i]
	pq[i].index = i
	pq[j].index = j
}

func (pq *priorityQueue) Push(x any) {
	item := x.(*pqItem)
	item.index = len(*pq)
	*pq = append(*pq, item)
}

func (pq *priorityQueue) Pop() any {
	old := *pq
	n := len(old)
	item := old[n-1]
	item.index = -1
	*pq = old[:n-1]
	return item
}